In recent years, with advances in the compression coding technology for media data such as video and audio, techniques for manufacturing optical disks and magnetic disks and recording/playback techniques, it has become possible to record media data of several hours on an optical disk or magnetic disk, and play back the same. In the case of a DVD (Digital Video Disc, or also called Digital Versatile Disc) which is now rapidly coming into wide use, a movie of about two hours can be recorded on an optical disk, by using MPEG2 or the like as the compression coding method, and played back. In addition, it is expected that a DVD recorder having functions which are equivalent to those of a present VCR (Video Cassette Recorder) and are realized by an optical disk will be shortly made available. Hereinafter, a data structure in the DVD recorder as a prior art of the data playback apparatus and the operation of the recorder will be described.
FIGS. 11(a)–11(c) are schematic diagrams for explaining a data structure in the DVD recorder (see “DVD Specifications for Rewritable/Re-recordable Discs Part3 VIDEO RECORDING Version 1.0, September 1999”).
FIG. 11(a) shows an entire data structure in a DVD, which is composed of a DVD_RTAV folder 1101, a management data file 1102, a movie data file 1103, a still-picture data file 1104, and an audio data file 1105. The DVD_RTAV is a folder which contains the files 1102–1105. The management data file 1102 includes entire information of the DVD such as the title text and updated date, and information concerning each program included in the DVD. Here, the program is one playback unit, i.e., a broadcast program. For example, news, a baseball relay broadcast, a movie and the like are programs, respectively. The management data file 1102 includes the title, creation date, playback duration, start address of the movie data file and the like, as information concerning each of the programs. The movie data file 1103 is a file which is obtained by concatenating plural programs. One example of the movie data file 1103 is shown in FIG. 11(b). In this example, the movie data file 1103 is composed of three programs, i.e., a first program 11031, a second program 11032 and a third program 11033. In the movie data file 1103, as shown in FIG. 11(c), compressively coded data of audio and video are multiplexed in units referred to as “PACK”. The size of a pack in the DVD recorder is fixed at 2048 bytes. In the still-picture data file 1104, plural pieces of compressively coded still-picture data are multiplexed in units of pack. This is used as data for a slide show in which display images are switched at prescribed periods. In the audio data file 1105, compressively coded audio data are similarly multiplexed in units of pack. This is for use on the postrecording to movie data.
FIG. 12 is a diagram for explaining an example of program playback when the second program 11032 shown in FIG. 11(b) is to be played. Address information for indicating from which byte in the movie data file 1103 the playback is to be started is recorded in the management data file 1102, for each program. Therefore, when the second program 11032 is to be played, start address information 1201 of the second program is initially extracted from the management data file 1102 and, in accordance with this start address information, the reading position of the movie data file 1103 is moved to a position indicated by the start address information 1201. Then, the data are read out, whereby the playback can be started from the second program.
In order to perform high-seed searching playback of a program or program searching playback, information of reading positions in the movie data file at intervals of about one second is included in the management data.
Next, the program erasure in the DVD recorder is described with reference to FIG. 13. In FIG. 13, numeral 1103 denotes a movie data file before program erasure, which is composed of three programs in this case. Assuming now that the second program 11032 is to be erased, the third program 11033 is concatenated immediately after the first program 11031, as shown by reference numeral 1303. Simultaneously, the information concerning the second program 11032 is also erased from the management data file.
In the above descriptions, the outlines of the data structure in the DVD recorder and the operation for playing or erasing a program are given.
As described above, in the DVD recorder as the prior art data playback apparatus, the media data such as video and audio are recorded as a movie data file in which plural programs are concatenated. The object to concatenate plural programs as one file is to make the best use of the capacity of a disc. However, in this data structure, the following problems occur.
Initially, it is required to extract start addresses of all programs to decide reading positions of the movie data file in the management data file, and as a result, the structure of the data playback apparatus is complicated. Further, when the number of programs is increased, there is a risk that the size of the management data becomes enormous due to the start address information. In portable information terminals using MPEG4 as the latest media data compression coding technology, the coding bit rate of media data is assumed to be approximately 64˜384 Kb/sec., which is some-tenths as large as the coding bit rate of a DVD using MPEG2, or smaller. Further, in the portable information terminals, it is assumed that media data is obtained by radio communication. It is expected that the playback time of one program becomes relatively short, for example, approximately some dozen seconds to some minutes, to suppress the communication charges. Therefore, there is a possibility that the number of programs recorded on one disc is substantially increased.
In addition, upon the erasure of a program, a process of concatenating unerased programs to recreate a movie data file is required. Since the portable information terminal uses a secondary battery such as a lithium ion, the above-mentioned program concatenation/recreation processing reduces the utilization time at one charge, thereby decreasing the user's operability.